枚举类

如下注意点：

1. 枚举类不能有public构造方法

2. 枚举值可以调用相应的构造方法

3. 枚举值可以调用抽象方法实例化

如下为自己通过一般的类来模拟enum的实现

public abstract class MyEnum {    private String name;    private MyEnum(){}    private MyEnum(String name){        this.name = name;    }    public static MyEnum MON = new MyEnum("星期一") {        @Override        public MyEnum nextDay() {            return TUES;        }    };    public static MyEnum TUES = new MyEnum("星期二"){        @Override        public MyEnum nextDay() {            return WED;        }    };    public static MyEnum WED = new MyEnum("星期三") {        @Override        public MyEnum nextDay() {            return null;        }    };    public abstract MyEnum nextDay();}